Free Phenolic OH Research Articles

Effect of postharvest drying on physicochemical properties, volatile yield, composition, and sensory attributes of Alpinia zerumbet (shell ginger) rhizome

Alpinia zerumbet or shell ginger, an essential oil-bearing rhizomatous native herb of Southeast Asia belongs to the family Zingiberaceae. The rhizome has high culinary value and is profusely used as a spice, food additive, in cosmetics and others. The current study was conducted to investigate the effect of six postharvest drying treatments (shade, sun, freeze, microwave, and oven drying at a temperature of 40 °C and 60 °C) on physicochemical properties, volatile yield and compositions, and sensory attributes of shell ginger. In contrast to other drying methods, freeze drying showed better water activity, rehydration capacity and retained the usual color and micro-structure of sliced rhizomes. FTIR analysis of dried rhizome powders revealed the corresponding banding for C-O-C stretching, CC stretching, CH2 asymmetric stretching and free phenolic OH stretching respectively. The maximum yield of essential oil was obtained in freeze drying (0.028%), followed by fresh rhizomes (0.02%), and the minimum yield was recorded in microwave drying (0.003%). The GC-MS analysis of rhizome oil reported 4-terpineol (31.89–46.85%), eucalyptol (14.28–23.74%), γ-terpinene (2.19–6.67%), fenchyl acetate (5.01–11.21%), o-cymene (2.99–14.92%), and β-pinene (2.18–5.05%) as the principal volatile constituents which were significantly affected by the six drying methods. Spicy and camphoraceous aroma were dominant in fresh and dried rhizome essential oil accessions with traces of pine and lemon odor. The fresh rhizome oil negatively affected the germination rate and inhibited the shoot and root length of wheatgrass seeds with IC50 values of 882.55, 87.79 and 72.2 µg/mL respectively showing its mild phytotoxic potential. These findings demonstrated the freeze drying as the most efficient postharvest technique to preserve the natural qualities of shell ginger and laid down a basic experimental framework for further value addition and industrial feasibility.

A prodrug of 3-(ferrocenylaminocarbonyloxymethyl)phenol activated by reactive oxygen species in cancer cells

Hybrid drugs containing ferrocene and phenol residues, whose π systems are not conjugated with each other, exhibit potent anticancer activity as previously reported. Few important open questions are remaining before practical application of these drugs becomes possible. First, their mode of action is not fully clarified. Second, it is not known whether these drugs exhibit cancer cell specificity. Third, due to the presence of the phenol moiety, these drugs can potentially be oxidatively deactivated and eliminated via phase II metabolism when applied in vivo. In this paper we report on synthesis of three prodrugs of aminoferrocene-phenol hybrids, where the phenolic OH group is masked as a boronic acid pinacol ester. We confirmed that the best prodrug in this small series p5 is activated in human ovarian cancer A2780 and Burkitt's lypmphoma BL-2 cells, but remains inactive in representative normal SBLF9 cells. Since p5 does not contain free phenolic OH groups, it will not be metabolized as phenols in vivo. We confirmed that the mechanism of anticancer activity of aminoferrocene-phenol prodrug p5 relies on generation of reactive oxygen species in cells.

Synthesis, Characterization and Antioxidant Activity of Two Novel Oxovanadium (IV) Curcuminoids

The reaction of bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) and two novel ligands of bis[4- tetrabenzylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetrabenzylglucose)curcumin) (BTBGC) and bis[4-tetraacetylglucose- 3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetraacetylglucose)curcumin) (BTAGC) with vanadium in methanol, in a 2:1 molar ratio, which yield the complexes of ML2 where M is [VO]2+, have been synthesized and characterized by FT-IR, mass spectrometry, 1H NMR spectroscopy and elemental analysis. These novel compounds were also examined for their antioxidant activity (using Trolox Equivalent Antioxidant Capacity (TEAC) antioxidant assay as a measure of their overall ability to scavenge free radicals compared to antioxidant standards such as Trolox); compounds with free hydroxyl groups were more active than those one whose locking such and also the metal complexes showed more activity than Trolox. The antioxidant capacity was decreased in BTBGC, BTAGC and their complexes compared to curcumin and its oxovanadium (IV) complex, corroborating the importance of curcumin’s free phenolic OH groups for scavenging oxidants potential. Also, the presence of the methoxy group increases the activity.

Alkylation of monomeric, dimeric, and polymeric lignin models through carbon-hydrogen activation using Ru-catalyzed Murai reaction

In this study, we have assessed directed carbon-hydrogen activation (CHA) for alkylation of monomeric, dimeric, and polymeric lignin models using Murai's catalyst [RuH2(CO)(PPh3)3]. Based on related work from our laboratory showing that isolated organosolv lignin bears benzylic directing groups ideal for CHA reactions, this approach could offer new methodology for the valorization of biorefinery lignin. Monomeric and dimeric models bearing a keto group at the benzylic position undergo Ru-catalyzed alkylation in good to excellent yield. Similarly, models bearing a benzylic OH group also undergo alkylation via a tandem oxidation/alkylation process enabled by the Ru catalyst. Polymeric models show low levels of functionalization as a result of the poor solubility of the starting polymer. With unsymmetrical models, functionalization occurs first at the least sterically hindered ortho-site, but a subsequent alkylation, leading to disubstituted products can occur at the more sterically hindered site, leading to hexasubstituted arenes. The reaction shows sensitivity to free phenolic OH groups, which appears to reduce the yield in some reactions, and is also a contributing factor to the low yields observed with polymeric lignin models. Combining CHA methodology with lignin isolation technology able to introduce appropriate directing groups for catalytic functionalization will form the basis for improved conversion of lignin to high value chemical products.

Synthesis, Characterization and Antioxidant Activity of Two Novel Oxovanadium (IV) Curcuminoids

The reaction of bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) and two novel ligands of bis[4- tetrabenzylglucose-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetrabenzylglucose)curcumin) (BTBGC) and bis[4-tetraacetylglucose- 3-methoxyphenyl]-1,6-heptadiene-3,5-dione (bis(tetraacetylglucose)curcumin) (BTAGC) with vanadium in methanol, in a 2:1 molar ratio, which yield the complexes of ML2 where M is [VO]2+, have been synthesized and characterized by FT-IR, mass spectrometry, 1H NMR spectroscopy and elemental analysis. These novel compounds were also examined for their antioxidant activity (using Trolox Equivalent Antioxidant Capacity (TEAC) antioxidant assay as a measure of their overall ability to scavenge free radicals compared to antioxidant standards such as Trolox); compounds with free hydroxyl groups were more active than those one whose locking such and also the metal complexes showed more activity than Trolox. The antioxidant capacity was decreased in BTBGC, BTAGC and their complexes compared to curcumin and its oxovanadium (IV) complex, corroborating the importance of curcumin’s free phenolic OH groups for scavenging oxidants potential. Also, the presence of the methoxy group increases the activity.

Functionalized Organosolv Lignins Suitable for Modifications of Hard Surfaces.

Two different organosolv lignins (OSLs), that is, wheat straw and corn stover OSLs, were chemically and enzymatically functionalized. Functional groups were attached via the formation of stable ether bonds exploiting the reactivity of free phenolic OH groups along the lignin backbone. The functional groups introduced a range from compact charged and chargeable building blocks for the generation of surface-active lignins to oligomeric and polymeric species used in lignin block-copolymer productions. Combination of selected functions led to novel charged or chargeable polymeric lignin-based materials. Products could be realized with different degrees of technical loadings in terms of introduced functional groups.

A Lewis‐Acid‐Catalyzed Phenolic Ether ‘O to C’ Rearrangement: Synthesis of 4‐Aryldihydrocoumarins

AbstractAn efficient O to C rearrangement of phenolic ethers is developed. The Lewis acid BF3⋅OEt2 (0.5 equiv) could catalyze the O to C migration of β‐aryloxy‐β‐arylesters to β,β‐bis‐arylesters, thereby the free phenolic OH cyclizes with the ester group, resulting in the formation of 4‐aryldihydrocoumarins.

A multifunctional tripodal fluorescent probe for the recognition of Cr3+, Al3+, Zn2+ and F− with controllable ESIPT processes

Three 4-(benzo[d]thiazol-2-yl)-2,5-dihydroxybenzaldehyde fluorophores were introduced to construct a tripodal multifunctional ESPIT fluorescence probe L. The fluorescent analysis revealed that probe L exhibited excellent recognition capabilities towards Cr3+, Al3+, Zn2+ and F− ions with large Stokes shifts. Furthermore, under optimal conditions, the detection limit of probe L towards Cr3+, Al3+, Zn2+ and F− were low, of the order of 10−8 M, which indicated that probe L was sensitive to these four ions. Interestingly, the fluorescent and 1H NMR titration experiments revealed that the recognition mechanism of probe L towards the ions Cr3+, Al3+, Zn2+ and F− were different. The presence of Cr3+ and Al3+ recovered the ESIPT, but the presence of Zn2+ trigger a moderate deprotonation of the phenolic OH and induced an ESIPT red-shifted (60 nm) emission wavelength. Finally, the presence of F− completely deprotonated the free phenolic OH and a remarkable red-shifted (130 nm) ESIPT emission was observed. In other words, the ESIPT process of probe L is controllable. Furthermore, the utility of probe L as a biosensor in living cells (PC3 cells) towards Cr3+, Al3+ and Zn2+ ions has been demonstrated.

Effect of steam explosion treatment on chemical composition and characteristic of organosolv fescue lignin

Tall fescue, a grass currently grown as forage, presents a good potential as a feedstock in the development of biorefining. In this study, combination of steam explosion and an acetic/formic acid “organosolv” pretreatments are applied on raw fescue to optimize lignin extraction yields and obtain specific products. In a first step, fescue is pretreated by steam explosion under severity factors from 1.4 to 4.2. These treatments allow hemicelluloses solubilization and open the lignocellulosic structure. Steam exploded solid residues are then treated with an acetic acid (50%)/formic acid (30%)/water (20%) mixture. Extracted lignins are precipitated and characterized by size exclusion chromatography (SEC), 31P NMR and HSQC NMR. Results show that acetic and formic acids extracted lignins present G, H and S units with ferulate and p-coumarate. Lignin typical linkages identified are of β-O-4 and spirodienone substructures. Combination of steam explosion and acetic and formic acid pretreatments increases extraction yields from 30% to 100%. Moreover, an increase of the steam explosion treatment intensity induces chemical modifications in lignin structure such β-O-4 and spirodienone substructure degradations, increase of free COOH and phenolic OH bonds, decrease of aliphatic OH ferulate and p-coumarate bonds and changes in G/H/S units proportions. Steam explosion intensity affects also lignin molecular weights.

Mononuclear, homo- and hetero-binuclear complexes of 1-(5-(1-(2-aminophenylimino)ethyl)-2,4-dihydroxyphenyl)ethanone: synthesis, magnetic, spectral, antimicrobial, antioxidant, and antitumor studies

A new Schiff base, H2L, was prepared by condensation of 4,6-diacetylresorcinol with o-phenylenediamine in molar ratio 1 : 1. The ligand reacted with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), oxovanadium(IV), and dioxouranium(VI) ions in the absence and presence of LiOH to yield mononuclear and homobinuclear complexes. The mononuclear dioxouranium(VI) complex [(HL)-(UO2)(OAc)(H2O)]·5H2O was used to synthesize heterobinuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H-, and 13C-NMR, electronic, ESR and mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal analysis. In the absence of LiOH, mononuclear complexes (1, 4, and 9) were obtained; in the presence of LiOH, binuclear complexes (3, 5, 7, and 10) as well as mononuclear complexes (2, 6, and 8) were obtained. In the mononuclear complexes, the coordinating sites are the phenolic oxygen, azomethine nitrogen, and amino nitrogen. In addition to these coordinating sites, the free carbonyl and phenolic OH are involved in coordination in binuclear complexes. The metal complexes exhibited octahedral, tetrahedral, and square planar geometries while the uranium is seven-coordinate. The antimicrobial and antioxidant activities of the ligand and its complexes were investigated. The ligand and the metal complexes showed antitumor activity against Ehrlich Acites Carcinoma.

ChemInform Abstract: Amyl Nitrite‐Mediated Conversion of Aromatic and Heteroaromatic Primary Amides to Carboxylic Acids.

Abstract A series of aromatic and heteroaromatic primary amides were converted directly to carboxylic acids by heating with amyl nitrite in acetic acid. Most conversions proceeded to give reasonable to excellent yields on a range of substrates containing various functional groups. This reagent system is thus applicable for the direct hydrolysis of a range of different primary carboxamides. The reaction with a phenolic aromatic substrate afforded two alternative nitration products as major outcomes, evidencing alternative reaction pathways resulting from the free phenolic OH.

Amyl nitrite-mediated conversion of aromatic and heteroaromatic primary amides to carboxylic acids

A series of aromatic and heteroaromatic primary amides were converted directly to carboxylic acids by heating with amyl nitrite in acetic acid. Most conversions proceeded to give reasonable to excellent yields on a range of substrates containing various functional groups. This reagent system is thus applicable for the direct hydrolysis of a range of different primary carboxamides. The reaction with a phenolic aromatic substrate afforded two alternative nitration products as major outcomes, evidencing alternative reaction pathways resulting from the free phenolic OH.

Structural Characterization of Lignin in Wild-Type versus COMT Down-Regulated Switchgrass

This study examined the chemical structural characteristics of cellulolytic enzyme lignin isolated from switchgrass focusing on comparisons between wild-type control and caffeic acid 3-O-methyltransferase (COMT) down-regulated transgenic line. Nuclear magnetic resonance (NMR) techniques including 13C, 31P, and two-dimensional 13C-1H heteronuclear single quantum coherence (HSQC) as well as gel permeation chromatography (GPC) were employed. Compared to the wild-type, the COMT down-regulated transgenic switchgrass lignin demonstrated a decrease in syringyl (S): guaiacyl (G) ratio and p-coumarate:ferulate ratio, an increase in relative abundance of phenylcoumaran unit, and a comparable content of total free phenolic OH groups along with formation of benzodioxane unit. In addition, COMT down-regulation had no significant effects on the lignin molecular weights during its biosynthesis process.

Eriosema chinense: A rich source of antimicrobial and antioxidant flavonoids

Six prenylated flavonoids, (2R,3S)-3,5,4'-trihydroxy-6″-6″dimethylpyrano(2″,3″:7,6)-8-(3″', 3″'-dimethylallyl)flavanone, (2R,3S)-3,5,2'-trihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavanone, (2R,3R)-3,5,2',4'-tetrahydroxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavanone, 3,5,2',4'-tetrahydroxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″',3″'-dimethylallyl)flavone, (2R,3R,2″'R)-3,5,2″'-trihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(3″'-methylbut-3″'-enyl)flavanone, (2R,3R)-3,5-dihydroxy-4'-methoxy-6″,6″-dimethylpyrano(2″,3″:7,6)-8-(2″',3″'-epoxy-3″'-methyl butyl)flavanone, an isoflavone, 6,7-dimethoxy-5,2',4'-trihydroxyisoflavone, and octaeicosanyl-trans-p-coumarate together with 12 known compounds, were isolated from roots of Eriosema chinense. This structural elucidation was determined by spectroscopic methods. Several isolates and derivatives were evaluated for their antimicrobial and antioxidant activities. Results obtained provide additional evidence showing that the presence of both the free phenolic OH and the lipophilic prenyl groups are crucial for potent antimicrobial activity against yeast, gram positive and gram negative bacteria, whereas the presence of free phenolic OH group is required for strong radical scavenging property.

Fragmentation mechanism of the phenylcoumaran-type lignin model compound by ToF-SIMS

Abstract The experiments with model compounds revealed that time-of-flight secondary ion mass spectrometry (ToF-SIMS) is able to split the common interunit linkages of lignin, except the 5-5 linkage. In a previous study, ToF-SIMS produced characteristic secondary ions with m/z 137 and 151 (C6-C1 fragments) from the phenylcoumaran-type lignin model compound, the benzofuran ring of which has a β-5 linkage and an α-O-4 linkage. However, it is still unclear whether the fragments are from ring A with the free phenolic OH as a result of the sole cleavage of the α-O-4 link by opening the furan ring or from ring B as a result of the β-5 cleavage. In this study, the phenylcoumaran-type lignin model compound and its deuterium- and/or 13C-labeled analogues were synthesized and analyzed by ToF-SIMS. It could be clarified that the β-5 linkage is not cleaved by ToF-SIMS.

Phenolic analogs of the N, C-coupled naphthylisoquinoline alkaloid ancistrocladinium A, from Ancistrocladus cochinchinensis (Ancistrocladaceae), with improved antiprotozoal activities

The first N,8′-coupled naphthylisoquinoline alkaloids with free phenolic OH groups, 4′- O-demethylancistrocladinium A and 6,4′- O-didemethylancistrocladinium A, have been isolated from the leaves and bark of the Vietnamese liana Ancistrocladus cochinchinensis, along with its known, non-phenolic parent compound, ancistrocladinium A, and four C, C-coupled representatives. The structure elucidation was achieved by chemical, spectroscopic, and chiroptical methods. The mono-phenolic alkaloid showed excellent activities in particular against the pathogen causing Chagas’ disease, Trypanosoma cruzi.

Biological Evaluation of Dilactone Lignan Analogues of Phellinsin A as Chitin Synthase II Inhibitors

).In conclusion, the effects of the number of free phenolic OH groups in dilactone lignan analogues of phellinsin A on inhibitory activities of chitin synthase II were examined for structure-activity relationships. Dilactone analogues lacking free phenolic OH functionality exhibited poor inhibitory acti-vities. Compounds possessing two free phenolic OH groups in each aryl group of dilactone

Cooperative Recognition of a Copper Cation and Anion by a Calix[4]arene Substituted at the Lower Rim by a β‐Amino‐α,β‐Unsaturated Ketone

We report herein a new ditopic calix[4]arene receptor 25,27-bis-{[4-amino-4-(1-naphthyl)-2-oxo-3-butenyl]oxy}-26,28-dihydroxycalix[4]arene (2) for the simultaneous complexation of anionic and cationic species. The host molecule 25,27-bis{[3-(1-naphthyl)-5-isoxazolyl]methoxy}-26,28-dihydroxycalix[4]arene (1) was synthesised first and was followed by a [Mo(CO)6]-mediated ring-opening reaction to give the target receptor 2. The binding properties of ligands 1 and 2 towards metal ions in CH3CN were investigated by UV/Vis and fluorescence spectroscopies. The results showed that both ligands 1 and 2 were highly selective for Cu(II) ions. Upon titration with Cu(II), the fluorescence of 1 was severely quenched, whereas 2 showed strong fluorescence enhancement because the metal ions help to lock the conformation of the fluorophores. During the complexation of 2 with Cu(II), the Cu(II) was reduced to Cu(I) by the free phenolic OH of 2, whereas the phenol was oxidised by Cu(II), after which it assisted in the trapping of Cu(I). Ditopic behaviour was observed for the complex 2.Cu(I), which showed further enhancement of its fluorescence intensity upon complexation with anions such as acetate or fluoride.

Biological Evaluation of Phellinsin A Analogues as Chitin Synthase II Inhibitors

Chitin is the β-1,4-linked homopolymer of N-acetyl-Dglucosamine (GlcNAc) that constitutes an important structural component of the cell walls of nearly all zoopathogenic and phytopathogenic fungi, and plays a crucial role in the determination of cell morphology. Chitin have been known to be synthesized by chitin synthase I, II, and III in Saccharomyces cerevisiae. Chitin synthase II is an essential enzyme for the formation of primary septum between mother and daughter cells, and chitin synthase III is responsible for the formation of chitin ring at bud emergence, whereas chitin synthase I is a repair enzyme of the damaged cells on cell division. Accordingly, specific inhibitors of chitin synthase II and III are expected to be an attractive target for the development of antifungal agents. In the course of exploring a chitin synthase II inhibitor from microbial sources, we isolated a new phenolic lignan bearing a γ-lactone ring from the cultured broth of Phellinus sp. PL3. The lignan compound named phellinsin A (3a) exhibited inhibition of chitin synthase II with an IC50 value of 27 μg/mL and showed 2.5 times stronger inhibitory activity than polyoxin D, and its structure was established by NMR analysis and synthesis. Our efforts toward the development of a potent antifungal agent have focused on examining structure-activity relationships for phellinsin A. We have modified the aryl group in phellinsin A by changing the number of phenolic OH groups in order to investigate the effect of the number of free phenolic OH groups in γ-lactone analogues of phellinsin A (3a) on chitin synthase II inhibitory activity. Herein, we describe the biological evaluation of phellinsin A analogues 3. The γ-lactone analogues 3c-f of phellinsin A were prepared by oxidative dimerization of cinnamic acid derivatives 1 into the corresponding dilactones 2, followed by monohydrolysis of the dilactones as shown in Scheme 1. The γlactones 3a and 3b were prepared by demethylation of compounds 3d and 3e using BBr3, respectively. The γ-lactone analogues 3 of phellinsin A were examined for structure-activity relationships of phellinsin A (3a). Inhibitory activities of the compounds against chitin synthase II were evaluated by measurement of the formation of chitin with UDP-[C]-N-acetyl-D-glucosamine. Table 1 showed the inhibitory activities of phellinsin A analogues at 140 and 280 μg/mL concentrations. The activities were largely dependent on the presence of free phenolic OH substituents in γ-lactone analogues 3. Generally, the compound 3f with non-phenolic OH groups did not show

Synthesis and characterization of dual function vanadyl, gallium and indium curcumin complexes for medicinal applications

Novel bis[4-hydroxy-3-methoxyphenyl]-1,6-heptadiene-3,5-dione (curcumin) complexes with the formula, ML 3, where M is Ga(III) or In(III), or of the formula, ML 2 where M is [VO] 2+, have been synthesized and characterized by mass spectrometry, infrared and absorption spectroscopies, and elemental analysis. A new ligand, bis[4-acetyl-3-hydroxyphenyl]-1,6-heptadiene-3,5-dione (diacetylbisdemethoxycurcumin, DABC) was similarly characterized; an X-ray structure analysis was performed. Vanadyl complexes tested in an acute i.p. testing protocol in STZ-diabetic rats showed a lack of insulin enhancing potential. Vanadyl complexes were, however, more cytotoxic than were the ligands alone in standard MTT (3-[4,5-dimethylthiazole-2-yl]ate, -2,5-diphenyl-tetrazolium bromide) cytotoxicity testing, using mouse lymphoma cells. With the exception of DABC, that was not different from VO(DABC) 2, the complexes were not significantly different from one another, with IC 50 values in the 5–10 μM range. Gallium and indium curcumin complexes had IC 50 values in the same 5–10 μM range; whereas Ga(DAC) 3 and In(DAC) 3 (where DAC = diacetylcurcumin) were much less cytotoxic (IC 50 = 20–30 μM). Antioxidant capacity was decreased in VO(DAC) 2, Ga(DAC) 3, and In(DAC) 3, compared to vanadyl, gallium and indium curcumin, corroborating the importance of curcumin’s free phenolic OH groups for scavenging oxidants, and correlated with reduced cytotoxic potential.